FCC Riser Feed Distributors for Uniform Catalyst-Oil Contacting
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Solution Overview
Problem
In fluid catalytic cracking (FCC) processes with larger riser diameters, distributing hydrocarbon feed evenly to mix with catalyst is challenging, leading to inadequate conversion and increased coke deposition due to uneven catalyst and oil contacting, resulting in lower conversion and higher dry gas production.
Innovation Solution
The implementation of a fluid catalytic cracking apparatus with at least two feed distributors positioned at the same elevation but at different radial distances from the riser wall, ensuring deeper penetration and more uniform distribution of the hydrocarbon feed, which improves catalyst-oil contacting and reduces coke deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single feed distributor is used in a large diameter riser, then the structure is simple, but the feed distribution is uneven and conversion is insufficient
Solution Approach 1:
The riser is divided into multiple feed distribution zones by using multiple feed distributors positioned at different radial distances from the riser wall. Each distributor handles a specific radial zone, ensuring comprehensive and uniform feed distribution across the entire riser cross-section, thereby improving conversion rates without requiring excessive complexity.
Solution Approach 2:
Different feed distributors are positioned at different radial distances from the riser wall to create localized feed distribution zones. This allows each distributor to optimize its spray pattern and penetration depth for its specific radial position, ensuring uniform feed-catalyst contacting across all regions of the riser.
2Manufacturing precision
If feed distributors are positioned at different radial distances, then feed distribution uniformity improves, but the positioning complexity increases
Solution Approach 1:
Feed distributors are positioned at different radial distances from the riser wall to create localized feed distribution zones. This allows each distributor to optimize its spray pattern and penetration depth for its specific radial position, ensuring uniform feed-catalyst contacting across all regions while maintaining a systematic positioning pattern that manages complexity.
Solution Approach 2:
The feed distributors are arranged in an asymmetric pattern with different radial positions rather than uniform spacing. This asymmetric arrangement optimizes feed distribution uniformity by accounting for the radial velocity profile and catalyst flow patterns in the riser, achieving better mixing efficiency despite the increased positioning complexity.
3Productivity
If feed penetration depth is increased, then catalyst-oil contacting improves, but the risk of coke deposition increases
Solution Approach 1:
The feed distribution function is segmented across multiple distributors at different radial positions. Each distributor provides moderate penetration depth optimized for its radial zone, collectively achieving thorough catalyst-oil contacting without excessive penetration that would cause vapor annulus formation and subsequent coke deposition in the riser center.
Solution Approach 2:
The spray parameters (penetration depth, spray angle, flow rate) of each feed distributor are optimized according to its radial position. Distributors at different radial distances use different spray parameters to achieve uniform catalyst-oil contacting efficiency across all zones while preventing the conditions that lead to coke deposition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This arrangement enhances feedstock conversion and catalyst-oil interaction, leading to improved conversion rates and reduced dry gas production, optimizing the FCC process, especially in larger units with riser diameters greater than 1.3 meters.
Implementation Method 1
Hydrocarbon feed distributors spray dispersion steam and hydrocarbon feed into the riser at a tip exit velocity with a horizontal component across the riser. However, a relationship between injected feed velocity, drop size and momentum limits the horizontal travel of the injected hydrocarbon feed against the lift gas and catalyst accelerating vertically, upwardly in the riser.
Implementation Method 2
As the oil vaporizes and cracks to form lighter products, the overall volume expansion causes a vapor annulus that travels vertically up the riser.
Implementation Method 3
As the oil vaporizes and cracks to form lighter products, the overall volume expansion causes a vapor annulus that travels vertically up the riser.
Implementation Method 4
The momentum of the liquid to vapor expansion causes the catalyst nearer the center of the riser to be pushed into a higher density stable column. The result is three distinct reaction zones.
Data Source
AI summary
An FCC process and apparatus may include injecting hydrocarbon feedstock at different radial positions while at the same elevation inside a riser. Multiple distributors may be used to position the tips for injecting feedstock at multiple radial positions. The distributors with tips more deeply positioned in the riser will penetrate a dense catalyst column we discovered generates in risers of larger diameter over 1.3 meters.